The SR540 is the newest addition to the SR family of coffee roasters. Roast capacity is 4 scoops or approximately 120 grams. It has an improved control board. All adjustments are made with pushing the knob and turning to adjust the heat, fan, and time. It also features a real-time temperature read out. A quick turn of the knob to the right will display current temperature. There are now 9 levels of heat adjustment compared to having a Low, Medium, and High adjustment. The fan also has a wider range of adjustment. The chaff basket and top lid from earlier SR roasters will not fit on the new SR540. The roasting chamber is a much larger diameter. Users are also able to change the default start settings.